Synergistic Effects of Oxaliplatin, 5-Fluorouracil, and Novel Synthetic Uracil Analog U-359 on Breast Cancer Cell Carcinogenesis.

Breast cancer presents significant global challenges, necessitating effective treatments to combat drug resistance and minimize chemotherapy side effects. This study evaluated the cytotoxic effects of U-359, Oxaliplatin (Ox), and 5-Fluorouracil (5-FU) in MCF-7 and MCF-10A cells using MTT and RealTime-GLO assays. Morphological changes were assessed by light microscopy following Wright-Giemsa staining. Apoptosis induction was studied using qPCR for apoptotic markers, the RealTime-Glo™ Annexin V assay, and the cleaved PARP1 ELISA assay. Caspase 8 and 9 activities, ABCB1, ABCG2, and NF-κB protein levels were quantified using ELISA. Synergy was analyzed using the Bliss Independence Model. The results indicated that combining U-359 with Ox and 5-FU enhanced cytotoxicity compared to individual treatments. U-359 induced apoptosis-associated morphological changes in MCF-7 cells, which were augmented with the Ox and 5-FU treatment. Apoptosis assays confirmed the up-regulation of pro-apoptotic markers and the down-regulation of anti-apoptotic markers with U-359 alone or in combination. Elevated cleaved PARP1 levels suggested robust apoptosis induction with U-359 and Ox or 5-FU. Caspase activity assays demonstrated a significant activation of caspase 8 and 9, implicating both apoptotic pathways. Furthermore, U-359 down-regulated ABCB1, ABCG2, and NF-κB in MCF-7 cells, which were up-regulated by Ox and 5-FU alone. The Bliss Independence Model revealed strong synergistic interactions (SI < 1) between U-359 and Ox or 5-FU, particularly in reducing ABCB1 and NF-κB levels. U-359 combined with Ox and 5-FU shows potential for overcoming chemotherapy resistance in breast cancer by enhancing apoptosis and modulating drug resistance. Further clinical studies are needed to optimize treatment and improve outcomes.